This invention relates generally to methods of forming front panels of room air conditioner units and the like and more particularly to a method of molding front panels provided with louver-like air intake grills each formed by a large number of transverse slats inclined with outward-upward slope.
In general, a room air conditioner unit operates to draw thereinto room air through an air intake grill formed in a front panel of the unit, to cause the air thus drawn in to pass through a heat exchanger within the unit and thus be cooled, and to discharge the cooled air into the room interior. A widely used air intake grill of an air conditioner unit of this type has a louver-like structure comprising a large number of transverse or horizontal slats disposed parallelly at specific spacing intervals. A typical method of fabricating this intake grill is to form the intake grill integrally with the front panel by injection molding a plastics material such as a polystyrene resin or an acrylonitrile-butadiene-styrene (ABS) resin.
In this case, the pin-point gates for injecting the molten resin into the mold cavities are positioned on the back face sides of the transverse grill slats. For this reason, the runners, constituting passageways for the resin within the mold, are ordinarily installed so as to direct the resin to the rear side through gaps between adjacent transverse slats. In such as case wherein the transverse slats are horizontal, it is possible to install the pin-point gates on the back faces of the slats, but, in the case where the transverse slats are inclined with upward slope, the spacing in the vertical direction between the front edge and the rear edge respectively of each pair of adjacent slats becomes very small. For this reason, it becomes difficult to provide the runners between the slats and to install the pin-point gates on the rear edge side of the slats.
Accordingly, in the conventional injection molding process, pin-point gates communicating with runners are installed at a plurality of positions within the mold corresponding to suitable positions on the front faces of the transverse slats or uprights or vertical members supporting and joined to the slats, as will be briefly described again hereinafter. The sprue resin material remaining in these pin-point gates after molding is cut off and removed by means of a trimming tool such as a trimming knife or a trimming nipper cutter.
Since the pin-point gates in a conventional mold are installed in this manner on the front face side of the front panel, cut marks due to the trimming of the surplus resin in these pin-point gates are left on the front exterior face of the front panel and, being unsightly, impair the aesthetic appearance of the front panel. As a consequence, the quality and commercial value of the product is lowered. Furthermore, if the diameter of the pin-point gates is reduced in order to reduce as much as possible the unsightliness of these cut marks, the injection flow of the molten resin will become poor, with the consequence that the required molding time will increase, and the process will become unsuitable for quantity production.
In order to solve these problems, it has been the practice heretofore to mold the intake grill and the supporting frame separately. In this method, a pair of film gates for forming injection inlets for the molten resin are provided on both sides of the intake grill, and the surplus resin remaining in these film gates after molding is trimmed off and removed. In the practice of this conventional method, however, it becomes necessary to use a plurality of molds, and the production cost rises. At the same time, the work of trimming and removing the film gates is difficult.